The material collected by Compton was rather fragmentary and poorly preserved, but Sahni was able to produce a fairly exhaustive work on the morphology and anatomy of this plant which was submitted to the London University as a part of his D.Sc. thesis in 1919 and published one year later in the Philosophical Transactions of the Royal Society.

Although Coulter and Chamberlain (1917) placed Acmopyle in the Taxineae and the same procedure was followed by Chamberlain (1935) in his book on Gymnosperms, Sahni's work has made it clear that this genus is very similar to Podocarpus in the vegetative anatomy of the root, stem and leaf. Marked similarities also exist in the structure of the male cones, microsporophylls and pollen grains, the drupaceous character of the seed, and the organization of the female gametophyte and young embryo. The only important differences between the two genera are that in Acmopyle the mature seed is nearly erect, the epimatium is fused to the integument even in the region of the micropyle, and the vascular supply of the ovule is much better developed than in Podocarpus. Taking the sum total of the characters, however, it was clear that Acmopyle had to be classed in the Podocarpaceae, perhaps as one of its most highly specialized members.

In the theoretical part of the paper Sahni proposed a division of the Gymnosperms into two broad groups: (a) Phyllosperms, with seeds borne upon the leaves; and (b) Stachyosperms, with seeds borne either directly upon an axis or upon a structure which is probably some modification of an axis. The Phyllosperms included the Pteridosperms and Cycadales (also the Caytoniales), and the Stachyosperms included the Cordaitales, Ginkgoales, Coniferales, Taxales and Gnetales. The position of the Bennettitales remained doubtful owing to the uncertainty regarding the morphological nature of their ovule-bearing stalks. As remarked by Florin (Botanical Gazettel, 1948) Sahni's view that these two groups constitute a natural assemblage receives considerable support from the results of recent researches on the morphology and phylogeny of the Palaeozoic and Mesozoic conifers.

An important point here is the breaking up of the stele and the formation of gaps without any influence from leaf traces which in normal fern rhizomes have been held to be the dominating factors in the evolution of a dictyostele.

Soon after the publication of his papers on Nephrolepis, Sahni submitted a dissertation for the Sudbury-Hardyman Prize on the "Evolution of Branching in the Filicales" which was published in the New Phytologist of 1917. In this he showed that as a rule the branches do not hold any regular position with respect to leaves and those cases where such a relationship is found”, this association is, in its evolutionary origin, a secondary phenomenon attributable to possible biological advantages, one of which may be the protection of the young bud ".

New Caledonia shares with some other islands of the Pacific the possession of a large number of endemic species which are of great interest to the morphologist and systematist. Prof. R. H. Compton of South Africa, who visited these islands in 1914, collected a number of plants among which was also the rare and little known conifer Acmopyle pancheri. Originally named by Pancher as Podocarpus pectinata, then renamed by Brongniart and Gris (1869) as Dacrydium pancheri, this plant was finally transferred by Pilger to a new genus of doubtful affinity. The generic name Acmopyle, which he gave to it, refers to the so-called apical position of the micropyle although actually it is not quite so.

The material collected by Compton was rather fragmentary and poorly preserved, but Sahni was able to produce a fairly exhaustive work on the morphology and anatomy of this plant which was submitted to the London University as a part of his D.Sc. thesis in 1919 and published one year later in the Philosophical Transactions of the Royal Society.

Although Coulter and Chamberlain (1917) placed Acmopyle in the Taxineae and the same procedure was followed by Chamberlain (1935) in his book on Gymnosperms, Sahni's work has made it clear that this genus is very similar to Podocarpus in the vegetative anatomy of the root, stem and leaf. Marked similarities also exist in the structure of the male cones, microsporophylls and pollen grains, the drupaceous character of the seed, and the organization of the female gametophyte and young embryo. The only important differences between the two genera are that in Acmopyle the mature seed is nearly erect, the epimatium is fused to the integument even in the region of the micropyle, and the vascular supply of the ovule is much better developed than in Podocarpus. Taking the sum total of the characters, however, it was clear that Acmopyle had to be classed in the Podocarpaceae, perhaps as one of its most highly specialized members.

In the theoretical part of the paper Sahni proposed a division of the Gymnosperms into two broad groups: (a) Phyllosperms, with seeds borne upon the leaves; and (b) Stachyosperms, with seeds borne either directly upon an axis or upon a structure which is probably some modification of an axis. The Phyllosperms included the Pteridosperms and Cycadales (also the Caytoniales), and the Stachyosperms included the Cordaitales, Ginkgoales, Coniferales, Taxales and Gnetales. The position of the Bennettitales remained doubtful owing to the uncertainty regarding the morphological nature of their ovule-bearing stalks. As remarked by Florin (Botanical Gazettel, 1948) Sahni's view that these two groups constitute a natural assemblage receives considerable support from the results of recent researches on the morphology and phylogeny of the Palaeozoic and Mesozoic conifers.